不同连作年限番茄根系淀积物的变化及其与根结线虫的关系

Variation of Rhizodeposits under Monocropping of Tomato and Its Relationship with Root-knot Nematode

了解蔬菜连作与土传病虫害的关系有助于发展绿色农业。基于根系淀积物在植物-土壤之间功能反馈中的重要地位,选择野外定位试验中番茄第2、第6和第8茬的不同连作年限处理,研究根结线虫的变化及其与土壤性质特别是根系淀积物组成的关系。结果显示:与第2茬相比,连作茬数增加导致土壤pH显著降低(P<0.05),而土壤有机碳和硝态氮含量显著升高;同时,根系淀积物的组分类别及其相对含量也有显著变化,其主要组分中有机酸类物质的数量和相对含量随连作茬数的增加而增加。土壤化学性质、根系淀积物和根结指数三者的网络结构分析表明,根结指数与网络中其他节点之间的联系伴随连作年限而增强。在第8茬中,根结指数与月桂酸含量呈负相关,与土壤NO3^--N含量以及颠茄碱、麦角甾醇的含量呈正相关,说明连作番茄根结线虫病害加重与土壤化学性质尤其是根系淀积物的变化有密切联系。

【Objective】This paper aimed at understanding the relationship between continuous monocropping of vegetable and soil-borne diseases,which will contribute a lot to development of green ecological agriculture.【Method】Based on the important role of rhizodeposition in plant-soil functional feedbacks,a field experiment was carried out to study incidence variation of root knot nematode diseases and explore its relationships with rhizospheric soil properties,especially composition of rhizodeposits in tomato fields under monocropping for 2,6 and 8 seasons and the same cultivation management.【Result】Results show that compared with the plot of 2 season,the plots of 6 and 8 seasons were significantly lower in soil pH(P<0.05),and significantly higher in concentration of soil total organic carbon and nitrate nitrogen.Root knot index of the tomato and incidence of the root knot nematode disease increased with the monocropping going on.A total of 150 kinds of rhizodeposits were identified with the gas chromatography/time of flight mass spectrometry(GC/TOF-MS)metabolomics,including alcohols,organic acids,amino acids,carbohydrate,terpenes,alkaloids and steroids compounds.Meanwhile,with the monocropping going on,composition and relative contents of the components of the rhizodeposits varied significantly,and the amount and relative abundance of organic acids,such as 3-(3-hydroxyphenyl)propionic acid,salicylic acid,thymol,succinic acid,lauric acid,as main components of the rhizodeposits increased,too.The network architecture analysis of soil chemical properties,rhizodeposits and root knot index shows that the network was reducing in complexity,but intensifying in modularization after continuous tomato monocropping.The compounds in the rhizosphere were quite closely related to soil chemical properties and root knot index of the tomato.Among them,3-(3-hydroxyphenyl)propionic acid,salicylic acid and succinic acid were negatively related to soil pH,and 3-(3-hydroxyphenyl)propionic acid,salicylic acid and atropine were positively to concentration of soil NO3^--N.The relationships between root knot index and other nodes were strengthened with the monocropping going on.【Conclusion】In the plot of 8 season,the root knot index was negatively related to content of lauric acid but positively to concentration of soil NO3-N-,atropine and ergosterol.The findings shows that the monocropping of tomato aggravates root knot nematode disease,which is closely related to soil chemical properties,especially variation of the rhizodeposits.Therefore,more efforts should be made in future studies,based on screening of key differential compounds,to specify,through simulation of the composition of the rhizodeposits,functions of specific compounds in the rhizosphere and their synergic effects with biological and abiotic factors on incidence of root knot nematode diseases.